An analysis of Chandra ACIS data for two relatively bright and narrow portions of the northwestern rim of G266.2 - 1.2 ( a.k.a .
RX J0852.0-4622 or Vela Jr. ) reveal evidence of a radial displacement of 2.40 \pm 0.56 arcsec between 2003 and 2008 .
The corresponding expansion rate ( 0.42 \pm 0.10 arcsec yr ^ { -1 } or 13.6 \pm 4.2 % kyr ^ { -1 } ) is about half the rate reported for an analysis of XMM-Newton data from a similar , but not identical , portion of the rim over a similar , but not identical , time interval ( 0.84 \pm 0.23 arcsec yr ^ { -1 } , 37 ) .
If the Chandra rate is representative of the remnant as a whole , then the results of a hydrodynamic analysis suggest that G266.2 - 1.2 is between 2.4 and 5.1 kyr old if it is expanding into a uniform ambient medium ( whether or not it was produced by a Type Ia or Type II event ) .
If the remnant is expanding into the material shed by a steady stellar wind , then the age could be as much as 50 % higher .
The Chandra expansion rate and a requirement that the shock speed be greater than or equal to 1000 km s ^ { -1 } yields a lower limit on the distance of 0.5 kpc .
An analysis of previously-published distance estimates and constraints suggests G266.2 - 1.2 is no further than 1.0 kpc .
This range of distances is consistent with the distance to the nearer of two groups of material in the Vela Molecular Ridge ( 0.7 \pm 0.2 kpc , 43 ) and to the Vel OB1 association ( 0.8 kpc , 25 ) .